Coatings of polymeric materials on various substrates are of industrial significance and provide the basis for a number of products. It is generally recognized that adhesion of polymeric coatings to substrates is critically important in determining the properties and performance characteristics of a coated article. Unfortunately, the nature of adhesion between a polymeric coating and a substrate tends to be complex and often difficult to test, study, or control (Adhesion Measurement of Thin Films, Thick Films and Bulk Coatings; Mittal, K. L., Ed.; 1978, pp 5-17).
One accepted method of improving the adhesion of polymers to inorganic substrates is to use silane coupling agents that contain groups reacting with inorganic surfaces as well as groups that react with the polymeric coating, Plueddemann J. Adhesion 1970, 2, 184. For example, the improved adhesion of crosslinked polybutadiene coated on glass plates treated with vinyltriethoxysilane compared to glass plates treated with ethyltriethoxysilane is illustrative of this effect, Ahagon et al. J. Polymer Science, Polymer Physics Edition 1975, 13, 1285. However, chemical application of silane coupling agents to various substrates tends to be a complex process that often requires a heat curing step. Further, it is generally difficult to limit the application of these coupling agents to selected areas of substrate, Arkles Chemtech 1977, 7, 766.
U.S. Pat. No. 4,503,140 describes photocurable coatings comprising organic polymers containing transition metal carbonyl species useful for printing plate formulations. The radiation cured coatings were crosslinked through polymer bound nucleophilic groups to form insoluble crosslinked resins. A wide variety of substrates are described as suitable for the coatings, including wood, paper, organic polymers, glass, ceramics, and metals.
U.K. Patent No. 1,463,816 describes organometallic metal carbonyl compounds useful for photocrosslinking of halogen containing polymers. Benzenechromium tricarbonyl and related metal carbonyl complexes photocrosslink polymers carrying a variety of nucleophilic groups. Oxygen was required for the crosslinking to proceed. The feasibility of binding organometallic polymers to a variety of surfaces has been questioned, Pittman Chem. Tech. 1971, 416.
Organometallic compounds have been used in chemical vapor deposition (CVD) processes to prepare films of metals, metal carbides, metalloids, ceramics, and the like. In general, the organic ligands of the organometallic precursor are lost in the CVD process as, for example, in the deposition of molybdenum/manganese alloy films from gaseous cyclopentadienylmolybdenum tricarbonyl manganese pentacarbonyl as described in U.S. Pat. No. 4,510,182. In some cases, organic groups may be retained in the bulk of the deposited films as, for example, in the photoelectrochemical decomposition of methylcyclopentadienylmanganese tricarbonyl onto soda-lime glass surfaces to leave a manganese film that was nonconducting due to incorporation of the cyclopentadienyl ligand, George et al. Thin Solid Films 1980, 67, L25. Precursor molecules in a CVD process must be sufficiently volatile to allow transport of their vapors to the substrate. Polymeric organometallic species, due to their high molecular weight and nonvolatile nature, are generally not suitable for film formation by CVD processes.
Pyrolysis of organometallic polymers, especially those incorporating main group metals or metalloids, has led to useful ceramic materials. For example, coatings of polysilazanes have been converted to silicon nitride ceramics (Seyferth et al. Inorganic and Organometallic Polymers, ACS Symposium Series; Zeldin et al. Eds.; 1988, pp 143-55) and organometallic polyesters of titanium have been pyrolyzed to TiO.sub.2 (Carraher Chem. Tech. 1972, 741). However, high temperatures are required for those transformations.
Organometallic complexes have been used to attach transition metal species to a variety of surface groups on inorganic supports for use as heterogeneous catalysts. Several mechanisms have been proposed for this reactivity. For example, catalytically important ruthenium tricarbonyl groups are thought to be attached to magnesium oxide supports by two Ru--O--Mg bonds and one MgOH--Ru bond. Cyclopentadienylmanganese tricarbonyl derivatives have been intercalated into a zirconium hydrogen phosphate host by a photolytic reaction.
Many organic polymers that incorporate transition metal carbonyl species by covalent bonds are known in the art. These polymers often have unique properties intermediate between those of metals and organic polymers.
In general, the transition metal containing organic polymers are prepared by copolymerization of organic monomers with organometallic monomers. Functionalization of preformed polymers by reaction with organometallic compounds to yield transition metal containing organic polymers is less well known. Vinyl ferrocenes have been hydrosilylated with polyalkylhydrosiloxanes to give siloxane polymers with pendent ferrocene groups. However, the method has not been demonstrated for transition metal carbonyl compounds. Reaction of chromium hexacarbonyl with preformed polystyrene has been demonstrated as a means of preparing copolymers of styrene and (styrene)chromiumtricarbonyl.